An Israeli army bulldozer crushed an American peace activist to death in the Gaza Strip yesterday in what witnesses described as a deliberate killing. Rachel Corrie, 23, died as she attempted to prevent the military destroying homes in the Rafah refugee camp, one of the most dangerous in the occupied territories.

"She was standing on top of a pile of earth," said another activist, Richard Purssell, who was a few feet away. "The driver cannot have failed to see her. As the blade pushed the pile, the earth rose up. Rachel slid down the pile. It looks as if she got her foot caught. The driver didn't slow down; he just ran over her. Then he reversed the bulldozer back over her again. She was very courageous."

Other activists said the bulldozer had approached from several metres away and that Ms Corrie, who was wearing a brightly coloured jacket, was waving and they were shouting at the driver to stop but he ignored them.

Witnesses said another protester had been slightly injured about half an hour earlier when the same bulldozer knocked him into barbed wire.

Ms Corrie was one of eight foreign volunteers - four from the US and four from Britain - with the International Solidarity Movement (ISM) seeking to block house demolitions.

Mr Purssell, from Brighton, said that earlier an Israeli tank protecting the bulldozer had attempted to drive protesters away with warning shots and teargas. But there had been no trouble immediately before Ms Corrie was crushed.

Doctors at al-Najar hospital said she had died from skull and chest fractures. The Israeli military described the death as a "very regrettable accident".

"We are dealing with a group of protesters who are acting very irresponsibly, putting everyone in danger - the Palestinians, themselves and our forces - by intentionally placing themselves in a combat zone," the army said.

An Israeli military official later claimed there was limited visibility, especially on the ground immediately in front of the vehicle, from the windows of the armoured bulldozers used by the army.

ISM volunteers frequently act as human shields to hinder demolitions, delay the construction of the new "security" wall in the West Bank or to help protect Palestinians harvesting their crops under threat from Jewish settlers.

An ISM spokesman in America said yesterday that Ms Cor rie was a student in Olympia, Washington, who had been in the area for about a month.

She is the first foreign peace activist killed in the occupied territories during the past 2 years of intifada.

Another witness, Mansour Abed Allah, a Palestinian human rights worker in Rafah, said it was ironic that an American should be killed by a US-made bulldozer: "America is providing Israel with tanks and bulldozers, and now they killed one of their own people."

In an email this month, Ms Corrie described a February 14 confrontation with another Israeli bulldozer in which she referred to herself and other activists as "internationals".

"The internationals stood in the path of the bulldozer and were physically pushed with the shovel backwards, taking shelter in a house," she wrote. "The bulldozer then proceeded on its course, demol ishing one side of the house with the internationals inside."

After her death, the movement called on the US government, the UN and the international community "to uphold international law and respect the Geneva convention". It also demanded that the US halt the sale of weapons and Caterpillar bulldozers used in the destruction of Palestinian buildings.

Rafah refugee camp is surrounded by Jewish settlements and army posts. Palestinian civilians say they are frequent victims of random shootings by the military and settlers. Children are often among the dead.

The Israeli military has imposed "full closure" on the occupied territories this week to coincide with the Jewish holiday of Purim. The order prevents any Palestinians crossing into Israel.